Classifying – separating – and assorting solids – Plural – diverse separating operations – Aqueous suspension and sifting
Patent
1985-04-30
1987-01-06
Bashore, S. Leon
Classifying, separating, and assorting solids
Plural, diverse separating operations
Aqueous suspension and sifting
209250, 209273, 209306, 209211, 162251, 210413, 210415, 2105123, B07B 120
Patent
active
046345213
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a screening apparatus for separating solid particles, such as fibre bundles used in paper making, and light particles from slurries, the apparatus comprising a vertical cylindrical screen; a rotor which is concentrically disposed inside the screen and the substantially closed outer surface of which together with the interior surface of the screen defines a screening zone for the pulp; an accept chamber surrounded by the outer surface of the screen; an inlet for supplying the pulp to be screened into the upper end of the screening zone; a reject chamber connected to the lower end the screening zone; and means for separating the heavy and the light impurities from each other.
BACKGROUND ART
When screening paper pulps containing a variety of impurities in a screen described e.g. in U.S. Pat. No. 3,363,759, the reject contains also particles which can be separated from it by employing centrifugal force. The particles separated in this way, the specific gravity of which is lower than that of the average particles, i.e. the light reject, contains e.g. various plastics. The remaining reject contains e.g. fibre bundles and pieces of knots. It is an object of the present invention to provide a screen which in a simple manner separates light impurities from the reject flow.
DISCLOSURE OF THE INVENTION
The screen to which the present invention relates has been developed from a known screen disclosed e.g. in U.S. Pat. No. 3,363,759. Another version of the screen of the patent has later been modified for removal of plastics, this apparatus in turn being disclosed in U.S. Pat. No. 3,912,622. In this version the separation of the light particles from the rejected pulp is arranged through a pipe one end of which is fixed to the inlet end of the screen and the other end extended through an opening in the cover of the casing. A conical extension is provided in the other end of the pipe which extends to the open upper end of the rotor. Due to the vortex movement of the rejected pulp the light reject concentrated in the inner part of the vortex flows out through a discharge pipe while the heavier reject gathered in the outer part is recirculated into the screening zone. In order to achieve efficient separation the reject flow must be ample, a fact which decreases the capacity of the machine.
It is an object of the present invention to provide a device simple in construction for separating light reject from the reject flow. This is achieved by arranging a pipe inside the rotor to remove the light reject, the upper end of the pipe being disposed adjacent to the inner surface of the closed upper end of the rotor. The invention provides a simple way of adding into existing screens a system for removing light reject.
BRIEF DESCRIPTION OF THE DRAWINGS
The apparatus according to the invention is illustrated by the accompanying drawings which are described in detail below.
FIG. 1 is a vertical section of an embodiment of the invention; and
FIG. 2 is a part of another embodiment of the invention.
BEST MODE OF CARRYING OUT THE INVENTION
The main parts of the screen illustrated in FIG. 1 are a multi-compartment housing 1, a screen drum 2, a rotor 3 and a shaft 4. The shaft is rotatably mounted inside the rotor on bearings on a cylindrical support 5 which is fixed to the housing by a sealing joint. The rotor is mounted on the upper end of the shaft and a belt pulley 6 on the lower end of the shaft for rotating the rotor. A disc 7 is fixed to the upper end of the support through which the shaft extends. The rotor outer surface 9 provided with half-spherical protrusions 8 and the inner surface 10 of the concentric screen drum defines a ring-shaped screening zone 11 where the pulp to be screened is fed into. The upper end of the rotor is closed by an end plate 12 into which the shaft is fixed.
The upper part of the housing constitutes of a feed chamber 13 provided with an inlet 4 for the pulp to be screened. There is a reject chamber 15 provided with a discharge orifice 16 in the
REFERENCES:
patent: 2510781 (1950-06-01), Howard
patent: 3363759 (1968-01-01), Clark-Powder
patent: 3726401 (1973-04-01), Bolton
patent: 3912622 (1975-09-01), Bolton
patent: 4268381 (1981-05-01), Hooper
Haapoja Vesa
Simola Markku A.
Ahlstrom Corp
Bashore S. Leon
Lithgow Thomas M.
Oy Wilh.Schauman AB
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